 The wilderness includes portions of the Darwin Plateau and the Darwin Hills.Much of the higher elevations are Tertiary volcanic rocks while the lower elevations to the southeast in Darwin Canyon are dominated by Permian marine sedimentary and metasedimentary rock.Though the wilderness is traditionally considered to be within the northern Mojave Desert, some classifications acknowledge floristic affinities with the colder deserts to the north and consider this the Southeastern Great Basin Ecoregion.. A desert scrub community is common in the wilderness with Joshua tree woodlands at higher elevations.